Interpretive Summary: New types of resins have recently been used to separate organic materials such as sugars and amino acids from soil and water organic matter. These small molecules must be removed from the larger humic substances--humic, fulvic, and XAD-4 acids--in order to study the processes by which they carry out their activities. Two methods of isolation were compared. The resin method gave better separations and information about origin of molecules than the older standard method. Ratios of the sugars can be used to show whether the sources are from plant or microbe origins. Microbes appear to be responsible for most of the sugar molecules present. The results of this research can be used by extension agents and agricultural consultants to make decisions on how soil and water quality is affected by fertilizers, organic wastes, and industrial chemicals entering into agroecosystems.

Technical Abstract:
The method for the isolation of the International Humic Substances Society standards from soils was compared with a procedure that used XAD-resin technology. Humic substances were isolated, using 0.1M sodium pyrophosphate at pH 7 (adjusted using 6M HCl), pH 10.6, and sodium pyrophosphate (0.1M)-sodium hydroxide (0.1M) pH 12.6. Sugar contents were greatest in the XAD-4 acids, and least in the fulvic acids (FAs). Neutral sugar contents in the humic acids (HAs) and FAs isolated by the two methods were similar. Based on the ratios of Gal+Man/Ara+Xyl, and Rha+Fuc/Ara+Xyl, it is suggested that the XAD-4 acids have significant inputs from microbial sources. Amino acid (AA) contents of the HAs isolated by both methods were similar.